1. Field of the Invention
The present invention relates generally to automotive headlamps, and more particularly to HID (high intensity discharge) automotive headlamps.
2. Disclosure Information
HID headlamps are commonly used nowadays in automotive applications, in large part because of the quality of light produced and because of the longevity, energy efficiency, and reliability of the lamp bulbs. Conventional automotive applications of HID projector-type headlamps are disclosed in U.S. Pat. Nos. 5,180,218 to Ohshio 5,709,451 to Flora et al., both of which are incorporated herein by reference. FIG. 8 (taken from FIG. 1 of the aforementioned Flora et al. patent) illustrates a representative prior art approach for constructing an HID headlamp for low beam conditions, which includes a light shield 20 with its top edge 22 positioned immediately beneath the second focal point F2 of the elliptical reflector 10.
In conventional HID automotive headlamp applications, the common practice is to provide two of such headlamps on each of the left-hand and right-hand front areas of the vehicle; one of these two headlamps per side would be a low beam headlamp similar to FIG. 8, while the other headlamp would be an essentially similar high beam headlamp that would not include a light shield 20. Besides the fact that the low beam headlamp has a light shield while the high beam does not, another difference between low and high beam headlamps is the respective forward-projected points in space ("hot spots") that each must be aimed at, as well as glare and intensity requirements. These requirements are specified by the Federal Motor Vehicle Safety Standard (FMVSS) and other automotive vehicle standards of the U.S. and other countries.
Although there are significant benefits in utilizing HID-type lighting systems in automotive applications, one drawback is the need for two headlamps per vehicle side. It would be desirable to provide an HID-based lighting system for automotive headlamp applications which requires the use of only a single headlamp per vehicle side.